1. Field of the Invention
The present invention relates to a prediction control method for predicting a condition of an apparatus to be controlled and controlling the apparatus based on the result of the prediction, and a prediction control device realizing this method.
2. Description of the Related Art
In recent years, a prediction control method has been employed for controlling an apparatus. The method includes predicting a variation in a parameter representing a condition of the apparatus and controlling the apparatus based on the result of the prediction. Such a method is disclosed, for example, in Japanese Laid-Open Patent Publication No. 4-205604, titled "A prediction control method of a process and a prediction control system". The prediction control system disclosed in this document will be briefly described as follows.
FIG. 20 is a configuration of the disclosed prediction control system which is adopted to control the main steam temperature of a thermoelectric power plant. A steam temperature prediction system 30 predicts a near-future value of the steam temperature using a steam temperature model expressed by a differential equation based on the law of conservation of mass and the law of energy conservation. The plant is controlled based on the result of the prediction.
Such a conventional prediction control system as shown in FIG. 20 has disadvantages as follows. When it is difficult to clearly specify the characteristic of a parameter for a condition of an apparatus to be controlled, a model expressed by an equation is not available. As a result, high-accuracy prediction cannot be obtained. Especially in the case where the characteristics of a plurality of parameters are interrelated, frequently it is impossible to express the characteristic of one parameter by an equation. Further, in the case where the value of a parameter cannot be extracted at a real time or in a periodic manner, an accurate value of a variation in the parameter is not obtained. This makes it difficult to use a model expressed by a differential equation which requires variations in a parameter measured at significantly short intervals.